The number of private tech companies valued at $1 billion or more has surged so much this year that on average 1.3 so-called unicorn companies have been created every week in 2015, according to data from CB Insights.

The past several years of raising too much, too high, too soon has run smack into a much more conservative investor ethos. Later-stage tech startups can still raise growth equity — and still lots of it — but not necessarily at the terms they were receiving just two months ago.

“This shift is only five or six weeks old, so most companies haven’t felt it yet,” a senior tech banker explains. “But I know of many companies who raised money at $1 billion valuations last year that are now being told that, to raise money now, they need to take around $700 million or $800 million. Probably with some serious structure that protects investors, like ratchets, on top of it.”

It should be noted that Primack is one of the best reporters on private equity and venture capital. He’s really plugged in, and he’s not an alarmist.

There’s been a growing sense that the Fed could soon raise interest rates, which would impact startup investing. More importantly: Successful VC-backed tech sector IPOs have been few and far between. Just this week, flash-storage provider Pure Storage went public, but began trading below its $17 IPO price, and closed the day at $16.01.

The public markets are more harsh than private markets. This means private investors need to reset their expectations, which is leading to downward valuation pressure.

It certainly seems like this is the beginning of the downturn in the private tech sector that VCs like Benchmark’s Bill Gurley have been warning about for a year now.